These include major players identified in studies of learning and memory such as the BDNF transcriptional activator CREB, the ubiquitous signaling kinase CaMKII (CAMK2), essential for synaptic and structural plasticity [67], the cyclin-dependent kinase 5 (CDK5) gene which is implicated in stress responses and cocaine abuse [40,41,44], and the glutamate receptor GRIA1-4 genes that underlie synaptic potentiation during learning [59,60,65,68]. This evidence concerns the gene BDNF and cocaine abuse.